1. Field of the Invention
The present invention relates to an improved composition and method for detecting fibrinogen, fibrinogen split products and/or fibrin split products in blood by utilizing a suspension of killed, dyed Staphylococcus aureus cells.
2. Description of the Prior Art
The determination of fibrinogen, fibrin split products and fibrinogen split products in blood using Staphylococcus aureus cells is known:
It has been shown that staphylococcal cells contain two types of coagulase: a free coagulase form and a bound coagulase form. The free coagulase causes clotting of fibrinogen when it is liberated into a culture medium. However, while the bound coagulase or clumping factor is not released from the bacterial cell and therefore cannot cause clotting, it will cause a "clumping" phenomenon in the presence of fibrinogen. This "clumping" phenomenon has not been definitely characterized but appears to be caused by a precipitation reaction or localized clotting of fibrin on the Staphylococcus aureus cell wall which results in "clumping". (Duthrie, E. S., J. Gen. Microbiol. 10: 427-436 (1954) and Duthrie, E. S., J. Gen. Microbiol. 13: 383-393 (1955).
Hawiger, J., et al., J. Lab. Clin. Med. 75: 93-108 (1970), disclosed that, of the two types of split products which are formed during fibrinogenolysis, only the early split products cause clumping with Staphylococcus aureus cells. The early split products include fibrin monomers, fibrinogen split products and fibrin split products which are formed as the first hydrolytic products resulting from the action of plasmin on fibrinogen or fibrin. The early split products are relatively large peptides, whereas the late split products, formed by continued hydrolysis of the early split products, are smaller peptides. Late fibrin split products and late fibrinogen split products do not cause clumping with Staphylococcus aureus cells. A slide test method as well as a tube test method for determining the staphylococcal clumping characteristics of the various split products formed during fibrinogenolysis are described by Hawiger et al.
Leavelle, D. E., et al., Am. J. Clin. Path. 55: 452-457 (April, 1971), proposed a modification of the method of Hawiger et al.: microtiter plates are used in order to serially dilute the serum test samples (as well as the fibrinogen standards) for the determination of fibrinogen, fibrin monomers and fibrinogen split products in blood by means of staphylococcal clumping characteristics.